A control arrangement is known from U.S. Pat. No. 3,915,500 which utilizes a series of boom-type guide linkages extending between roof supports and a longwall face conveyor. The guide linkages have headpieces which are pivotably coupled to brackets on the goaf or stowage side of the conveyor and the operating position of a plough guided along the conveyor is controlled with the aid of upstanding hydraulic piston and cylinder units acting on the headpieces. Each headpiece is connected to a pair of resilient rods or bars constituting the associated guide linkage. The guide linkages are mounted on the roof supports for longitudinal motion and for swinging in a plane perpendicular to the mineral face. Thus these linkages serve additionally to guide the roof supports when these are shifted up towards the mineral face as well as to transmit the forces which arise during shifting of the conveyor and the roof supports.
In another known control arrangement, also utilizing the known boom-type guide linkages, as described in U.S. Pat. No. 4,462,637 an articulated toggle lever system is connected between the headpiece of each guide linkage and the conveyor and a piston and cylinder unit serves to operate the lever system. In this case the hydraulic units extend parallel to the conveyor and more or less horizontally.
A further control arrangment described in DE-3,111,460 has piston and cylinders units also disposed in a horizontal disposition parallel to the conveyor each serving to transmit the necessary control forces to a pivotable lever mounted with a ball-and-socket joint to the headpiece of the associated guide linkage. The lever is constructed to move along an arcuate path with the aid of a pin sliding in a track. The forces which are to be transmitted are relatively high and this necessitates a particularly heavy and strong construction and relatively large dimensions.
An object of the invention is to provide an improved control means and arrangement for boom-type guide linkages which is particularly compact.